The aim of all extraction procedures is to separate cellular or fluid lipids from the other constituents, proteins, polysaccharides, small molecules (amino acids, sugars…) but also to preserve these lipids for further analyses. The preservation of proteins involves special precautions found in delipidation procedures.
There is a great diversity of methodologies because biological tissues are not similar when considering their structure, texture, sensitivities and lipid contents. Removing the non-lipids without losing some lipids is a complex challenge, extracting some specific lipids is not always reliable for other kinds of lipids.
The high sensitivity of the analytical methods needed for low amounts of extracted lipids requires the use of very pure solvents and clean glassware. The chemical nature of the extracted lipids must also be taken into consideration.
Furthermore, all lipids must be protected against degradation through oxidation by solvent, oxygen, enzymes in combination with temperature and light.